1. Field of the Invention
The present invention relates to a lock apparatus for a door, more particularly to a lock apparatus provided with a switch member that is operable from an inner side of a door and that prevents accidental locking of the door.
2. Description of the Related Art
A lock apparatus provided with a switch member that is operable only from one side of a door is known in the art. This kind of lock apparatus is typically installed on a door to a bathroom or a child""s room, and is operable from an inner side of the door to permit locking of the door only by a person inside the room. Once the switch member is accidentally moved to a locking position and the door is then closed while nobody is inside the room, the door could be undesirably locked. This problem is frequently encountered in the aforesaid conventional lock apparatus, and causes considerable inconvenience to the user.
Therefore, the main object of the present invention is to provide a lock apparatus that can prevent accidental locking of a door to which the lock apparatus is applied.
Accordingly, the lock apparatus of the present invention includes a lock housing, a spindle, first and second operating levers, a latch member, a switch member and a biasing spring. The lock housing has a mounting wall formed with a spindle hole. The spindle extends through the spindle hole in the lock housing, and has opposite first and second ends. The first operating lever has a coupling portion coupled co-rotatably to the first end of the spindle, and a lever portion extending from the coupling portion. The lever portion is operable to cause axial rotation of the spindle. The second operating lever has a latch-mounting portion which is coupled co-rotatably to the second end of the spindle and which is mounted rotatably on the lock housing about an axis of the spindle. The second operating lever further has a lever portion extending from the latch-mounting portion, and a radially extending engaging flange formed on the latch-mounting portion. The engaging flange has a peripheral edge formed with a notch. The lever portion of the second operating lever is operable to cause axial rotation of the spindle together with the latch-mounting portion. The latch member is mounted on the latch-mounting portion, and is rotatable together with the latch-mounting portion about the axis of the spindle. The latch member has a first end portion mounted pivotally on the latch-mounting portion of the second operating lever about a pivot axis transverse to the axis of the spindle, and a second end portion opposite to the first end portion. The second end portion of the latch member is pivotable about the pivot axis toward and away from the latch-mounting portion. The switch member is mounted movably on the mounting wall of the lock housing, and is disposed adjacent to the engaging flange. The switch member is formed with an engaging protrusion, and is movable relative to the lock housing between a locking position, in which the engaging protrusion moves into the notch in the engaging flange and engages the engaging flange so as to prevent axial rotation of the latch-mounting portion and prevent rotation of the latch member with the latch-mounting portion relative to the lock housing, and an unlocking position, in which the engaging protrusion is disposed externally of the notch and disengages the engaging flange to permit axial rotation of the latch-mounting portion, thereby permitting rotation of the latch member with the latch-mounting portion relative to the lock housing. The biasing spring biases the second end portion of the latch member away from the latch-mounting portion. The latch member is depressible to move the second end portion of the latch member pivotally toward the latch-mounting portion about the pivot axis against biasing action of the biasing spring so as to enable the second end portion to push the switch member and move the switch member from the locking position to the unlocking position when the switch member is disposed in the locking position prior to depression of the latch member.